Conventionally, a transmission including: a torque converter for transmitting a power of an engine (particularly a diesel engine); gears in a plurality of levels connected to the torque converter; and a multiplate wet clutch for switching these gears has been utilized as a transmission for a diesel railcar or the like (see the publication of Japanese Utility Model Registration No. 2565596 as Patent Literature 1). There has been also suggested a technique for improving a transmission efficiency in a transmission for a diesel railcar by employing a mechanical clutch in place of the above-described multiplate wet clutch (see Japanese Utility Model Application Laid-open No. Hei. 2-103555 as Patent Literature 2 and Japanese Patent Application Laid-open No. Hei. 1-220761 as Patent Literature 3).
In recent years, a twin clutch transmission has been put into practical use for automobiles (see Japanese Patent Application Laid-open No. 2003-269592 as Patent Literature 4 and Mitsubishi Motors Technical Review 2008, No. 20, pp. 31 to 34 as Non Patent Literature 1). This twin clutch transmission has been conventionally used also as a transmission for a racing car.